Introducer devices provide for access to the venous system and are employed for inserting medical devices such as catheters, guidewires, leads, infusion ports, dialysis ports, dialysis catheters, and others. A typical procedure for gaining access to the central venous system or the arterial system with an introducer is the Seldinger Introduction Method. The Seldinger Method provides for insertion of a needle into the vasculature of a patient. Once the needle is in the vessel, the physician aspirates the needle to assure that the needle is in the vessel, and to draw out air present in the bore of the needle. The syringe is removed and discarded. A guide wire is inserted through the needle, and the needle is removed over the guide wire. The introducer, which includes a dilator and the sheath, is placed over the guidewire and inserted into the vessel. With the introducer and wire guide in the vessel, the dilator and wire guide are removed leaving only the sheath in the vessel. The desired medical device is implanted through the passage of the sheath. The sheath is optionally removed from the medical device. The introducer device provides access to the vein or artery, and therefore control of bleeding and the intake of air is necessary, for example, through use of a valve.
The introducer devices are designed to be used with both large and small instruments, such as dilators and guidewires. However, it can be difficult to effectively seal against instruments over such a wide variety of diameters. Furthermore, seals which are effective against larger diameter instruments are often ineffective in allowing smaller, or relatively softer devices, or devices having relatively lower column strength to pass through the seal. In addition, devices which have fragile features may be difficult to transfer through the seal without damage to the features and/or device.
Accordingly, what is needed is an introducer assembly which can effectively seal against a wide variety of instruments without inhibiting the throughput of the instrument, or damaging the instrument. What is also needed is an introducer assembly which does not distract or interfere with the implantation process.